How to lose weight with a low carb diet in two weeks

Look at the Government’s Eatwell Guide and you’ll see that they recommend a third of our diet is made up of starchy foods (pasta, rice, bread) and a third fruit and vegetables.

That’s two thirds of your daily intake of food in the form of carbohydrates. Why, then, is there such a backlash against this essential macronutrient when it comes to weight loss?

The answer comes down to the way the body deals with carbohydrates.

In an ideal world, an individual will consume enough carbohydrate needed for their energy output, some storage and a healthy amount of fat, without being overweight. However, eat more carbohydrate than the body can use (as glucose in the blood stream) or store (as glycogen in the liver and muscle) and it gets converted into fat for long-term storage. In contrast, eat less carbs and your body turns to your pre-existing fat storage for energy.

Hence why diets like The Atkins, Dukan, Keto and South Beach diet all rely on the principle of carb restriction to achieve weight loss results.

Why does a low carb diet seem to result in weight loss quicker than others?

It’s all about water weight, says Dietitian and BDA Spokesperson Chloe Miles. “When you eat carbohydrates, your body stores it as glycogen in the liver and muscle.

"Your muscles store approximately 500g and your liver approximately 100g and it’s thought that every gram of glycogen in the human muscle is bound to 3g of water,” she says.

Cut out carbohydrates and you deplete this store, which results in weight loss. Some dieters report a 4-5lbs weight loss in just two weeks from a low carb diet.

When more carbohydrate is consumed than the body can use, it's converted into fat for storage. Credit: Getty Images

In the longer term, removing carbohydrates as a source of energy means your body uses fat and protein as its main source, aiding weight loss.

However, it's worth noting that the idea of ‘cutting out carbs’ is very broad and not always completely helpful. Carbohydrate is a big food group, consisting of fibre (vegetables, whole wheat, pulses), starch (bread, pasta, rice, potatoes) and sugar (fruit, honey,biscuits, chocolate). For the aspiring slimmer, not all carbs are made equal.

While fibre and some starches are generally considered ‘good’ forms that provide a slow and steady release of energy, sugar is more contentious, as it provides a huge spike in energy very quickly, which the body is less likely to burn off (unless you're about to do exercise).

What are the drawbacks of a low carb diet?

There are schools of thought that argue against low carb diets.

One of the primary gripes is that it is simply not practical for day to day living. The process of converting fat to energy (when carbohydrate is not available) is much slower, so dieters can be beset by feelings of fatigue.

The process also causes a build up of ketones, sometimes resulting in Ketosis. This is where dieters experience nausea and weakness. (The presence of ketones also accounts for the bad smelling breath that followers of low-carb diets often bemoan.)

And, what’s more, a study by The American Journal of Clinical Nutrition that randomly assigned 43 obese adults two different diets – one 15pc carbohydrate and the other 45pc – found that it was energy intake, not nutrient composition, that determined weight loss over a short time period. The inference here is that low carb diets lead to weight loss not because you're cutting out carbs, but simply because you end up eating less.

A study on 43 obese adults found that it was energy intake, not nutrient composition, that determined weight loss over a short time period.Credit: Anthony Devlin /PA

Beth Matthews, 27, lost 6lbs after following a low carb diet for two weeks. “I cut out rice, pasta, potato and bread - which featured in every single one of my meals - and replaced it with vegetable alternatives like courgetti and cauliflower rice,” she says.

While she felt slimmer immediately after cutting out starchy foods, Beth said that the weight loss wasn’t worth the side effects. “I thought the shakiness and light-headedness that I suffered with on the first day would improve as my body adapted, but it persisted for the whole two weeks. I never felt full up and I was constipated for the first time in my life.”

After the two weeks, Beth resumed a normal diet, re-introducing starchy foods, and very quickly regained the weight she’d lost.

Five tips on how to lose weight fast with a low carb diet

1. Be mindful of the timing of your carbohydrate intake

Look to consume carbohydrates before, during or after exercise. Ben advises that this keeps your blood sugar stabilised.

2. Take your body fat percentage into account

While people with higher fat percentage can benefit from their body reaching fat burning stage (when your body breaks down fat for energy in the absence of carbohydrates), people with lower body fat percentage are more likely to need their fat for insulation so will need to consume more carbohydrate.

3. Choose nutrient-rich, low starch foods

It’s important to watch your nutrient intake so try to avoid ‘empty calories’ that often come in the form of packaged foods. Fill up on fibrous, non-starchy vegetables such as dark leafy greens and ensure starchy vegetables are consumed around exercise.

4. Adopt ‘carbohydrate loading’ into your exercise routine

Completely exhausting your glycogen stores is damaging. Ben suggests introducing ‘carb loading’ days - where you’ll eat three times as many carbohydrates as a normal day - either the day before, or the day of exercise.

5. Keep a food diary

It’ll help break those heavily ingrained habits where carbohydrates are concerned.